Due to recent developments in information and communication technology, dielectric materials are becoming ever more important in determining the characteristics of communications circuits. Characteristics demanded by such dielectrics usually include (i) having an appropriately large relative dielectric constant (∈r) corresponding to the intended target in the microwave band; (ii) a small dielectric loss, i.e. a high quality factor (Q·f; wherein Q is the reciprocal of the dielectric loss tangent tan δ, and f is the resonance frequency); and (iii) a small absolute value of the temperature coefficient (τf) of resonance frequency.
Forsterite is known as one such dielectric ceramic. This substance consists of the reaction product (Mg2SiO4) of Mg and SiO2, and possesses comparatively excellent high-frequency characteristics.
The present inventors have previously developed a forsterite ceramic, which has a small dielectric loss in the microwave range, by controlling the impurities that are mixed in and the grain size of the powder during the forsterite production process (refer to Patent Document 1). The present inventors have also experimented with low-temperature firing, by adding 10% by weight or less of a rutile-type titanium dioxide (herein after sometimes simply called “titanium dioxide”) (refer to Patent Document 2).
[Patent Document 1]
Japanese Patent No. 3083638
[Patent Document 2]
Japanese Patent No. 3083645